OEMs seeking simple cost effective solutions to lower CO2 on existing and future vehicle programmes should consider changing wheels, according to Alcoa Wheel Products, a division of Alcoa, the world leader in the production and management of primary aluminium, fabricated aluminium and alumina. It suggests by switching to a forged alloy wheel, OEMs can achieve an immediate and significant saving in weight, which in turn can lower CO2. The lower weight can also offer further benefits to the OEM and the car owner including a performance and fuel efficiency gain.

Wheels have always been the focal point in exterior design aesthetics. With dimension creep and pedestrian safety legislation raising bonnet lines, particularly in Europe, wheels have been growing proportionally and subsequently increasing unsprung mass with inevitable consequences in ride comfort and CO2 emissions.

Cast alloy wheels can be produced cost effectively but Alcoa believes forging offers an immediate solution, even on an existing vehicle platform, where traditional weight saving programmes involve costly tooling and validation.

Alcoa Wheel Products has been at the forefront of developing, producing and supplying alloy wheels to the global automotive industry for 60 years. With the parent company involved in all elements of aluminium manufacture from mining to recycling, the firm believes it can extract maximum design benefit from the forging procedure. Forging is the process of forcing a solid billet of aluminium between forging dies under extreme pressure. As opposed to cast wheels, forging retains a better metal structure (alignment of the aluminium grain structure is retained) offering improved strength and durability, that with appropriate design can lead to a significantly lighter wheel.

Optimising savings

“Our analysis shows an optimised forged, as opposed to casted or two-piece alloy wheel, can actually save up to 39kg per car,” explains David Yates, marketing manager, Europe for Alcoa Wheel Products – Forged Speciality Wheels. “This is based on a 19-inch US SUV wheel but a recent programme in Europe for a sports car manufacturer demonstrated we could save close to 10kg compared to their current cast wheel.”

With stringent environmental legislation, Alcoa’s Engineers have recognised that a weight reduction of 45kg equates to a fuel economy improvement of 1.5 percent.

“Less unsprung weight can improve vehicle dynamics and reduce inertia,” claims Yates. “This is a further way to improve handling or acceleration with minimal cost and testing on an existing car and it’s more efficient to engineer a more compliant suspension with a lighter wheel.”

Cost benefits of forged wheels

While a forged wheel has a higher piece cost than a cast wheel, Yates is quick to point out that there are other cost benefits. “A single blank can be machined into five or six variants. OEMs can quickly refresh a car or offer a range of value-added accessory products with minimal tooling. We are already offering this in the US with a single blank delivering six different SUV wheels. Our eight-axis machining capability delivers a significant design and manufacturing advantage over the competition.”

The benefits of forged wheels are attracting growing interest in Europe, the most recent contract announced being for the one million Euro Lamborghini Reventón. Alcoa Wheel Products believes European OEMs are increasingly considering forged wheels to lower weight, increase performance or improve aesthetics. It is in this latter area that Alcoa Wheel Products is to announce further programmes with its Dura-Bright technology.

Research from customer satisfaction surveys suggests that wheel condition and maintenance are important to drivers and a major consideration in wheel design by OEMs.

Alcoa’s new Dura-Bright technology is being developed with the aim of enhancing the perceived quality by making wheels easy to clean, maintain and keep free from corrosion, and is making its automotive debut on the latest Audi A6. It is the latest innovation in aluminium from Alcoa, who first helped Audi pioneer the lightweight aluminium space frame on the original A8.

“It is clear that all OEMs require a new wheel solution that is durable while retaining a high quality, innovative finish,” claims Yates.

“By staying cleaner longer, Dura-Bright technology wheels enhance a vehicle’s appearance allowing Audi A6 owners to enjoy their vehicle while lowering maintenance efforts.”

Traditional alloy wheels rely on lacquer as a finish and protection against the elements. During heat cycling, brake dust and grime can penetrate the lacquer to create a permanent yellow discoloration and black specks. Dura-Bright technology penetrates the surface of the wheel to become an integral part of the aluminium itself. It resists peeling, cracking and corrosion while offering a premium finish in keeping with Audi’s vehicle design philosophy.

The technology has been offered in the commercial vehicle market since 2003, and fitment on the Audi A6, Shelby Mustang and Chrysler SRT vehicles signal the first automotive applications.

“By staying clean, Dura-Bright wheels enhance a car’s perceived quality as well as preserving the OEM’s reputation,” says Yates. “This will in turn improve resale value. Forged wheels can deliver benefits from concept right through the product life cycle.”